init

#init

##Syntax init

##Description The init (initialization) keyword is used for two different purposes in Turing. The most common is for initializing arrays, records and unions. The less common is for recording parameter values in subprograms for later use in post conditions.

##Example

    var mensNames : array 1 .. 3 of string :=
        init ( "Tom", "Dick", "Harry" )
    put mensNames ( 2 )             % This outputs Dick
    var names : array 1 .. 2, 1 .. 3 of string :=
        init ( "Tom", "Dick", "Harry",
             "Alice", "Barbara", "Cathy")
    put names ( 2, 1 )  % This outputs Alice

##Details The order of initializing values for multi-dimensional arrays is based on varying the right subscripts (indexes) most rapidly. This is called row major order. Initialization of records and unions is analogous to initializing arrays. Values are listed in the order in which they appear in the type. See array, record, and union types.

##Example This procedure is supposed to set integer variable i to an integer approximation of its square root. The init clause records the initial value of i as j so it can be used in the post condition to make sure that the approximation is sufficiently accurate. The name j can be used only in the post condition and nowhere else in the procedure.

    procedure intSqrt ( var i : int )
        pre i >= 0
        init j := i
        post abs ( i - sqrt ( j ) ) <= 1
        � statements to approximate square root�
    end intSqrt

##See also pre.html and post.html assertions and procedure.html and process.html declarations.